1. Field of the Invention
The present invention relates to a marking method and device which uses letterpress printing.
2. Prior Art
FIG. 4 shows one of the conventional marking devices.
In this device, a plate holder 51 to which a printing plate (rubber stamp) 50 is attached is installed on a plate holder attachment 52 so that the plate holder 51 can slide in the Y direction which is a direction perpendicular to a lever 54. The plate holder 51 is mounted on the plate holder attachment 52 via a screw 53.
The plate holder attachment 52 is inserted into the lever 54 which extends in the X direction. The attachment 52 is fastened via a screw 55.
The lever 54 is inserted into a moving block 56 which is driven by a predetermined amount in the vertical direction and in the X and Y directions via a driving means (not shown). The lever 54 is fastened in place by a screw 57.
In this device, the position of the printing plate with respect to the Y direction is adjusted by loosening the screw 53 and moving the plate holder 51 in the Y direction. The position of the printing plate 50 in the Z direction is adjusted by loosening the screw 55 and raising or lowering the plate holder attachment 52, and the position of the plate 50 in the ".theta." direction can be adjusted by loosening the screw 55, and moving the lever 54 in the horizontal direction.
Since the printing plate 50 is used in the prior art device, characters formed on the plate 50 become worn. As a result, the width of the printed characters changes and/or a discrepancy is generated in the printed character position.
In this case, according to conventional method, a sample of a printed character is picked up, and the printed character's width and any discrepancy in the printed character position are measured visually or by using a measuring instrument.
If any change in the width of the printed character is found, the screw 55 is loosened, the plate holder attachment 52 is raised or lowered for proper adjustments, then the screw 55 is tightened back. After this, printing is performed, and the printed character position is reexamined so that the printed character position is adjusted by repeating the above steps until the correct position is obtained.
If a discrepancy in the printed character position is found, the screws 53 and 57 are loosened, and the plate holder 51 and the lever 54 are moved in the Y and X directions, respectively. After this, the screws 53 and 57 are tightened back, printing is performed and then the printed character position is examined. Based upon the result of the examination, the printed character position is adjusted to the correct position by repeating the steps described above.
In the conventional method, however, a good quality printing can only be achieved by repeating the operations of (a) stopping the device, (b) measuring the printing condition, (c) mechanically adjusting the amount of lowering of the plate holder 51 and the Y direction of the holder 51 and (d) then performing the printing.
Thus, the measurement and adjustment cannot be performed unless the device is stopped. The correct values cannot be ascertained without performing a test printing after such an adjustment, and considerable time and skill are required to make such an adjustment.